We've rented twice - this year and last, 29'. Last time was the first time we had ever even been in an RV. We had reviewed their videos online, but there wasn't particularly much instruction given to us when we picked it up. The units have been in very good shape - super cold A/C, colder than our house, and that was for July in Florida. No problems with fridge, plumbing, etc. Both of the units were well-used, and while I wouldn't say they were dirty, they could have used a better cleaning. Bringing all our own linens and supplies made it okay. We have always gotten our deposit back completely.
We never used propane or the generator, and it has costed us $100/day. Miles are pretty expensive, so we didn't go far - just the Fort and relatively near state parks.
We love it - it is a great way to see Florida, and Ft. Wilderness is, by far, IMO the best resort in Disney. I would love to try one of the Fort RV rentals, but we like to do a couple of days at state parks as part of the vacation.
It seems like a great idea to call the rental place directly. I've always called the 1-800 number, but next time I will call the dealer directly and see if they can do a better price.